“Lots of animals are sensitive but human beings are extremely sensitive to it,” added Prof Buttner.

Image copyrightScience Photo Library

Isabel Bear and RG Thomas, the researchers who first named the scent petrichor, found that as early as the 1960s it was being captured to sell as a scent called “matti ka attar” in Uttar Pradesh, India.

Now, geosmin is becoming more common as a perfume ingredient.

“It’s a really potent material and it smells just like the concrete when the rain hits it,” said perfumer Marina Barcenilla. “There’s something very primitive and very primal about the smell.”

“Even when you dilute it down to the parts per billion range, [humans] can still detect it,” she added.

Yet we also have an odd relationship with geosmin – while we are drawn to its scent, many of us dislike its taste.

Even though it is not toxic to humans, the tiniest amount can put people off mineral water or wine when it is present.

“We do not know why we dislike geosmin,” commented Prof Jeppe Lund Nielsen from Aalborg University in Denmark.

“It is not toxic to humans in typical found ranges, but somehow we associate it with something negative,” he added.

Petrichor: The term:

Coined by scientists Isabel Joy Bear and Richard Thomas in their 1964 article “Nature of Argillaceous Odour”, published in the journal Nature.

The word was coined from Greek petros, meaning “stone”, and ichor, meaning “the fluid that flows in the veins of the gods”

Plants

According to Prof Nielsen, research also indicates that geosmin could be related to terpenes – the source of scent in many plants.

Image copyrightScience Photo LibraryImage captionTerpenes are commonly produced by conifers like pine

Rain could bring these fragrances out, says Prof Philip Stevenson, a research leader at Royal Botanic Gardens, Kew.

“Often the plant chemicals that smell pleasant are produced in leaf hairs… and the rain may damage these, releasing the compounds.

“Rain may also break dry plant material releasing chemicals in a similar way to when you crush dried herbs – the smell becomes stronger,” he told the BBC.

Very dry periods may also slow down plant metabolism, with renewed rainfall giving it a kick start and causing plants to release a pleasant scent.

Image copyrightScience Photo Library

Lightning bolts

Thunderstorms have their role to play too, creating the clean, sharp scent of ozone – caused by lightning and other electrical discharges in the atmosphere.

Prof Maribeth Stolzenburg of the University of Mississippi explains: “Besides the lightning, the thunderstorm and especially the rain will improve the air quality. Much of the dust, aerosols, and other particulates are rained out and the air clears.”

Related Articles

[ad_1] Media playback is unsupported on your device Media captionThe visualisation runs from January to December 2016 This colourful video tracks the behaviour of the ozone layer over Antarctica across all of 2016. It shows clearly the annual “hole” that appears above the South Pole in the austral springtime, and which last year grew to […]

Image copyright Mike Siva-JothyImage caption Up close, the mouthparts the bugs use to suck blood are clearly visible A study that began as an investigation into the “utterly bizarre” way in which bedbugs reproduce has revealed they have existed for far longer than humans. DNA samples from 30 species of bedbug revealed the insects had […]

Image copyright DOUG ALLAN/SCIENCE PHOTO LIBRARY. Part of the world’s largest ice shelf is melting 10 times faster than the rest, shedding light on how it might respond to climate change. The study of Antarctica’s Ross Ice Shelf reveals that one area is melting due to relatively warm ocean water getting into a cavity under […]